NASA announced that its next-generation J-2X engine will begin its second round of tests starting today.

The J-2X engine is a redesign of the J-2 engine that carried astronauts to the moon during the 1960s and 1970s. It was developed by Pratt and Whitney Rocketdyne, which were awarded a $1.2 billion NASA contract.

The J-2X is the first new liquid oxygen and liquid hydrogen rocket engine made in 40 years that will be able to send humans into space again. In fact, the J-2X engine is designed to power deep space missions and will be used for NASA's Space Launch System (SLS), which is a heavy-lift rocket intended for deep space missions.

Last year, NASA conducted the first round of testing on the J-2X engine, which resulted in successful test firings. In that particular round of sea-level tests, the J-2X engine was fired 10 times total for 1,040 seconds, reaching 100 percent power in just four tests. It also met a full flight-duration firing of 500 seconds in the eighth test, which proved to be quicker than any other U.S. engine.

Now, the J-2X is on to its second round of testing starting today. NASA will now simulate high-altitude conditions where there is lower atmospheric pressure. According to Tom Byrd, J-2X engine lead from NASA's Marshall Space Flight Center in Huntsville, Alabama, J-2X engines will be tested in the SLS' second stage of flight where nozzle data and overall performance will be monitored.

"We're making steady and tangible progress on our new heavy-lift rocket that will launch astronauts on journeys to destinations farther in our solar system," said Charles Bolden, NASA administrator. "As we continue test firings of the J-2X engine and a myriad of other work to open the next great chapter of exploration, we're demonstrating our commitment right now to America's continued leadership in space."

The United States' role in space has been a hot topic since NASA retired its space shuttle fleet last year. Since that retirement, American astronauts have been forced to depend on Russian Soyuz rockets to make their way to the International Space Station (ISS), where the cost of one seat on the Russian spacecraft is expected to increase to $63 million by 2015. The U.S. knew it had to find another way to the ISS without depending on Russia, so it jumped on the private space travel industry to fill in the gap.

SpaceX, which is expected to be the first private company to send a spacecraft to the ISS on May 7, stepped up with its Dragon cargo capsule in an attempt to fill the void of the space shuttle fleet.

With the U.S. back in the space race, NASA plans to test the J-2X engine throughout the rest of this year. The engine is currently on the A-2 Test Stand at NASA's Stennis Space Center in Mississippi.